Indexable cutting inserts

ABSTRACT

Indexable cutting inserts having a multiplicity of successively usable cutting edges, the inserts having pre-ground areas of circular cross-section formed by spin grinding directly in the rear of all of the cutting edges.

United States Patent [is] 3, 81,830 Dupuis 1 Aug. 8, 1972 [S4] INDEXABLECUTTING INSERTS 3,497,933 3/1970 3,116,538 H1964 [72] Inventor. HubertDupuk, Warren, Mich. 3,279,034 I 0/1966 [73] Assignee: Allegheny LudlumIndustries, lnc., 3,279,035 [0/1966 Pittsburgh, Pa. 2,278,738 4/ i942[22] Filed: 1970 Primary Examiner-Harrison L. Hinson [2!] Appl. No.:87,532 Attorney-Whittemore, Hulbert and Belknap Related US. ApplicationData [62] Division of Set. No. 725,445, April 30, 1968, 1571 ABSTRACT PO- lndexable cutting inserts having a multiplicity of successivelyusable cutting edges, the inserts having pre- [52] US. Cl ..29/95, 29/I05 ground areas of circular cross-section formed by spin [51] Int. Cl..B26d l/00, 826d 1] l2 grinding directly in the rear of all of thecutting edges. [58] FieldolSearch.........29/95, 96, 103, 105, 105 A[56] References Cited 8 Claims, 15 Drawing Figures UNITED STATES PATENTS3,486,210 12/1969 Greenleaf ..29/9$ saw 1 of z FIG- T HUB UPU E O FIG.8W I W 9 g ATTORYFYS INDEXABLE crm'mo msaa'rs 'copending application Ser.No. 725,445 filed Apr. 30,

1968, now U.S. Pat. No. 3,561,170.

BRIEF SUMMARY OF THE INVENTION In accordance with the present invention,commercially available inserts are mounted in a special rotary fixtureso that clearance or relief surfaces are provided in the rear of thecutting edges by rotating the fixture relative to a grinding wheel whichis either stationary or which may be oscillated to distribute thegrinding action over the required area of the insert.

The cutting inserts are accurately located in the fixture which is ofcourse formed with high precision mounting means corresponding preciselyto the mounting means formed in the tool holder or body in which theinserts are subsequently to be used. The inserts are indexed andreversed if appropriate, so that each of the cutting edges on the insertis formed with a high degree of accuracy and provided with the relief orclearance surface of circular cross-section. The operation not onlyprovides the cutting edges with the relief or clearance surfaces, butalso converts inserts of commercial tolerance to high precision insertsin which the cutting edges are located with whatever degree of accuracyand precision is required.

If the inserts are ground in a fixture having the same effective radiusof rotation for the cutting edges as will be employed in the cuttingtool, then of course the cutting edges are provided with relief surfacesof circular cross-section, either cylindrical or conical, of limitedwidth, the surfaces occupying the imaginary surface of rotation of thecutting edge. However, it is preferable to provide clearance in additionto the circular relief surfaces and this follows when the inserts arepositioned in a fixture having a smaller effective radius than theradius at which the cutting edges will operate in the cutting tool.Similar, but specifically different results are obtained when providingclearance in back of the cutting edge when the inserts are spun-groundin a fixture which, while having the same effective radius as the toolholder or body, positions the inserts at an angle different from theangle at which they will be positioned in the cutting tool holder orbody. Obviously, both the different radius and inclination may becombined simultaneously in a single operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of an indexableinsert constructed in accordance with the present invention.

FIG. 2 is a side view of the insert as seen from the right in FIG. 1.

FIG. 3 is a side view of the insert as seen from the front in FIG. 1.

FIG. 4 is a view similar to FIG. 1, showing a prespun insert of positiverake type.

FIG. 5 is a fragmentary diagrammatic view showing the manner in whichthe inserts are mounted on a cutter body.

FIG. 6 is a diagrammatic view illustrating the relationship of an insertin a special grinding fixture and a grinding wheel.

FIG. 7 is a diagrammatic view similar to FIG. 6, showing therelationship between a pre-spun ground insert when mounted in a cutterbody of larger diameter than the fixture in which the insert was ground.

FIG. 8 is a view similar to FIG. 6 showing an insert mounted in agrinding fixture at an angle different from the angle at which theinsert is to be used.

FIG. 9 is a diagrammatic view showing the relationship of the insert asground in FIG. 8, when positioned in a tool body of the same diameter asthe grinding fixture but at a different angle.

FIG. 10 is a fragmentary end edge view of an insert showing a relief orclearance surface of limited width provided in rear of the cutting edge.

FIG. 1 l is a view showing a grinding fixture having a plurality ofindexable inserts for grinding relief or clearance surfaces of circularcross-section in rear of a relatively short cutting edge locatedadjacent a corner of the insert.

FIG. 12 is a front elevational view of the arrangement shown in FIG. 11.

FIG. 13 is a view similar to FIG. 11 showing the provision of relief orclearance areas of conical configuration.

FIG. 14 is a view similar to FIG. 11 showing a modified method ofproducing relief or clearance of circular cross-section.

FIG. 15 is a fragmentary view similar to FIG. 12 showing the appropriateinclination of a reversible or cubical insert to provide appropriaterelief in rear of the cutting edges.

DETAILED DESCRIPTION Referring first to FIGS. 1-5 there is shown in FIG.I an indexable blade or insert 10 which may be formed of a suitable hardcutting material such for example as tungsten carbide. The indexableinsert 10 illustrated in FIGS. 1-3 is a flat body having planar sidesurfaces 12 and 14 and planar edge surfaces 16, 18, 20 and 22. Indexableinserts of this type may be square as indicated, triangular, pentagonal,hexagonal, or other shapes including circular cross-section. The presentinvention however, is directed to inserts having cutting edges formed bythe intersection of one or both of the flat side surfaces with the edgesurfaces modified as hereinafter disclosed.

It will be understood that in use the cutting inserts such as theinserts 10, are mounted in a rotary holder or tool body 24 havingrecesses 26 in which the inserts are received and in which they areclamped in operating position by suitable clamping means such forexample as wedge means illustrated at 28 in FIG. 5. The direction ofrotation of the holder 24 is indicated by the arrow and it will beobserved that in front of the cutting insert there is provided a recess30 which receives chips from the cutting operation. With the parts asillustrated in FIG. 5, it will be observed that a cutting edge isprovided generally at 32 which is formed by the intersection between thefront surface of the insert which may be the surface 12 or 14, and anedge surface thereof which may be the edge surface 16, 18, 20 or 22, thecutting edge being modified as hereinafter described.

Where the edges 16, I8, 20 and 22 are perpendicular to the side surfaces12 and 14, it will be understood that the insert is not only indexable,but is also reversible,

thus the square insert illustrated in FIG. 1 has eight successivelyusable cutting edges. With this insert it will be observed that theincluded angle of the cutting edge between the surfaces 12 or 14 on theone hand, and l6, 18, 20 or 22 on the other hand, is 90. Accordingly, aninsert of this type requires positioning in a rotary holder so that acondition of zero or negative rake exists. In other words, referring toFIG. 5, the front surface of the insert must either be radial withrespect to the cutter body, in which case a condition of zero rakeexists; or it must be inclined rearwardly in the direction of rotation,in which case a condition of negative rake exists.

In practice it is found that much superior results are obtained when thesurface directly in rear of the particular cutting edge in use is arelief or clearance surface of circular cross-section, eithercylindricalor conical, dependent upon the arrangement of the insert in the holder.In some cases the surface of circular crosssection directly in rear ofthe cutting edge may have a radius of curvature equal to the radius ofcurvature of the imaginary surface generated by the cutting edge uponrotation of the tool. In other words, the surface of circularcross-section directly in rear of the cutting edge may occupy thecylindrical or conical imaginary surface traced by the cutting edge uponrotation of the tool.

Preferably however, the surface of circular cross-section directly inrear of the cutting edge is in clearance or diverges inwardly from theimaginary surface generated by the cutting edge upon rotation of thecutter. This clearance may result from the fact that the surface ofcircular cross-section has a radius of curvature smaller than the radiusof the circular path generated by the cutting edge upon rotation of thetool. Alternatively, the clearance may result from the fact that thesurface of circular cross-section, while having a radius of curvatureequal to the radius of the path generated by the cutting edge duringrotation of the tool, nevertheless diverges inwardly because ofinclination of the insert, and more specifically because the center ofcurvature of the surface of circular cross-section lies forwardly of aline joining the cutting edge to the axis of the holder or tool body.

While it is perfectly feasible to modify inserts and to employ them incutters so that the surface of circular cross-section in rear of thecutting edge occupies an entire edge surface of an insert, it is moreusual to limit the circular cross-section relief or clearance surface toa relatively narrow band directly in rear of the cutting edge. Moreover,in many applications only a portion of an available cutting edge isused; namely, the portion adjacent one comer of the insert.

Referring again to FIGS. 1-3, the insert 10 has a total of eightclearance or relief surfaces of circular crosssection located directlyin rear of cutting edges, four of these surfaces being indicated inFIGS. 1-3 at 34, 35, 36 and 37. It will be observed that these areas aregenerally triangular in outline. It will be appreciated that fouridentical relief or clearance surfaces of circular cross-section areprovided which intersect the opposite side 14 of the insert, two ofthese being visible in FIG. 2 at 38 and 39, and an additional one beingvisible in FIG. 3 at 40. The exact shape and arrangement of these reliefor clearance surfaces will become more apparent in conjunction with adescription of the method of forming these surfaces.

Referring now to FIG. 4 there is shown an insert 42 having a flatsurface 44 at one side parallel to a similar flat surface at theopposite side, and provided with four inclined edge surfaces 45, 46, 47and 48. The side edges 45, 46, 47 and 48 converge as indicated in FIG. 4so that the insert is in the form of a relatively thin normal section ofa pyramid. In this type of insert the cutting edges are characterized inthat they have acute included angles, and accordingly, they are capableof being used in cutters with positive rake. However, with this type ofcutter, only four sequentially usable cutting edge portions areavailable. As seen in FIG. 4, corner portions of the edge surfaces 45,46, 47 and 48 are spun ground to provide relief or clearance surfaces49, 50, 51 and 52 which extend rearwardly from cutting edges. Thecutting edges after modification of course, are defined by theintersection between the adjacent flat side surface and the modifiededge surface portion which has been formed to circular cross-section,either cylindrical or conical.

Referring now to FIG. 6 there is illustrated the manner in which acutting insert 54 is spun ground. The insert is illustrated as locatedin a grinding fixture or holder 56 having a plurality of recesses 58 inwhich the inserts 54 are received in accurately located position. Thefixture S6 is rotatable and of circular cross-section so that an edgeportion or a part of an edge portion of the insert 54 extends radiallybeyond the holder into position to be engaged by the periphery of agrinding wheel 60. The edge surface 62 of the insert 54, or a portionthereof, is ground to circular cross-section by rotation or oscillationof the holder, causing the edge portion 62 of the insert to move in acircular path past the peripheral surface of the grinding wheel. It willbe apparent that this operation forms the edge surface 62 or a portionthereof to a cylindrically formed surface having an axis or center ofcurvature at 64 which is the axis of rotation of the holder 56. It is tobe observed that in the illustrated arrangement the front surface 66 ofthe insert occupies a plane radial with respect to the fixture 56.

It will of course be understood that the production of the pre-spunground inserts involves suitable indexing of the insert 54 so that allof the cutting edge portions thereof which are to be used are providedwith the relief or clearance area directly in rear of the cutting edge.It will further be observed that irrespective of any dimensionalirregularities in the insert prior to spin grinding, there will beproduced an insert after it has been spun ground in which the cuttingedges are located with a high degree of accuracy with respect to thelocating recess or pocket in which they are mounted in use.

Referring now to FIG. 7 there is diagrammatically illustrated the mannerin which the spun ground surface provided on the edge 62 of the insert54 affords clearance when it is mounted in a tool body or holder of adiameter greater than that of the grinding fixture 56. In this Figure,the portion of the circle indicated at 64 may be considered as theimaginary surface generated by the cutting edge 68 upon rotation of aholder or cutter body having an axis of rotation at 70. Assuming thatthe front surface 66 of the insert is caused to occupy a plane radial tothe cutter, then the clearance in rear of the cutting edge 68 increasesfrom the cutting edge to the trailing edge by an amount indicated at d.

It will of course be understood that in FIG. 7 there is no attempt toshow a holder such as the holder 24 of FIG. 4, but only to indicate thegeometry involved.

Referring now to FIG. 8 there is illustrated a somewhat differentprocedure in providing a clearance or relief surface of circularcross-section directly in rear of a cutting edge designated 72 providedon an insert 74. Here, the grinding fixture indicated at 76 is providedwith a locating recess 78 such that the insert 74 is inclined from theposition which the insert 54 occupies in FIG. 6. In other words, thefront surface 80 of the insert does not occupy the radial plane 82 ofthe fixture body. With a plurality of inserts carried by the fixture 76in the same position as illustrated for the insert 74, the grindingfixture 76 is rotated to cause the cutting edges 72 of the insert 74 totraverse the grinding wheel 84, thus forming surfaces of circularcrosssection, and in the embodiment illustrated, surfaces which arecylindrical, as a result of contact with the grinding wheel. Again, itis stressed that the actual area formed to circular cross-sectiondirectly in rear of the cutting edge may be a relatively narrow surfacesuch for example as from 0.005 to 0.125 inch.

Referring now to FIG. 9 the manner in which the clearance is introducedby suitable mounting of the modified insert 74 as produced by the setupillustrated in FIG. 8, is shown. Here, while the circle 86 indicatesthat the circular path traversed by the cutting edge has substantiallythe same diameter as the diameter of the grinding fixture 76, clearanceresults from the fact that the pockets or seats 88 formed in the cutterbody position the inserts 74 at a different angle from the angle whichthey occupy in the grinding fixture. Thus, as seen in FIG. 9, the frontsurface 80 of the insert 74 in the cutter body, occupies a radial plane90 thereof. Accordingly, the relieved edge surface 92 providesincreasing clearance from the cutting edge 72 rearwardly to the trailingedge by an amount designated d.

In FIG. there is illustrated a portion of an insert 94 having a cuttingedge 96 provided by the intersection of the front surface 98 and thesurface 100 which is of circular cross-section and is directly in rearof the cutting edge. In this Figure the edge surface 102 is the fiatunmodified edge surface initially provided on the insert. This Figureillustrates that the cylindrical or conical curvature provided in rearof the cutting edge may extend for only a very short distance rearwardlytherefrom.

Referring now to FIGS. 11 and 12 there is illustrated a somewhatdifferent arrangement of providing the cutting edges, and this in factis the arrangement which would be employed in producing the modificationof insert illustrated in detail in FIG. 4. Here, a rotary grindingfixture 104 is provided having a plurality of recesses or seats 106 forreceiving inserts 108 which are of the positive rake type having fourcutting edges located only at one side of the insert. As best seen inFIG. 11, the inserts are slightly inclined as for example at aninclination angle of approximately 3. The grinding fixture is rotatedabout the axis of drive shaft 110 and a grinding wheel 112 is provided,the axis of which is parallel to the axis of the drive shaft 110.Accordingly, as the inserts are spun by the fixture 104, the grindingwheel contacts only the limited areas 114 and form these areas intocylindrical surfaces the center of curvature of which coincides with theaxis of the shaft 1 10.

Referring now to FIG. 13 there is illustrated a somewhat different setupfor spin grinding inserts intended for use in holders or cutter bodiesfor the purpose of angle cutting, chamfering, or the like. In this casea rotary grinding wheel fixture 116 is provided rotatable about the axisof shaft 1 18. The fixture is provided with a multiplicity of insertlocating seats 120 which as illustrated, position the inserts 122 withcutting edge portions thereof 124 to extend at a substantial angle asfor example 45, to the axis of the shaft 1 18. The grinding wheel 126 isprovided in the position shown, rotatable about an axis parallel to itsperiphery 128. The grinding wheel may if desired be of a width equal tothe length of the edge of the insert or it may be narrower as shown andreciprocated back and forth in the direction of the arrow to extend itsgrinding action from end to end of the edge of the insert.

Referring now to FIG. 14 there is illustrated yet another variation insetup for spin grinding the inserts. In this Figure the grinding fixtureis indicated at 130 and is rotatable about the axis of shaft 132. Aplurality of locating seats 134 are provided for receiving inserts 136,the inserts being positioned with an outer cutting edge 138 thereofparallel to the axis of the shaft 132. In order to spin grind a portionof the edge to provide a surface of circular cross-section directly inrear of the cutting edge, the grinding wheel 140 is provided at theinclination shown so that its periphery extends at a small angle, as forexample, a few degrees, with respect to the edge surface 138 of theinsert.

Referring now to FIG. 15 there is shown the arrangement necessary toprovide for a clearance or relief surface in the rear of cutting edgesprovided on an insert designed for zero or negative rake operation. Bythis, reference is made to an insert in which the included angle betweenthe front operating face of the insert and the edge surface, suitablyrelieved, is 90. In this case the are 142 may be representative of aperipheral portion of a grinding fixture having inclined seats orrecesses 144 into which a plurality of zero or negative rake inserts 146are positioned. The center of curvature of the grinding fixture isindicated at 148 and a radial plane passing through the cutting edge 150of the insert which is undergoing treatment is indicated at 152. It willof course be understood that if the insert 146 is square, it willprovide eight cutting edges each of which must be spun ground in aseparate operation.

l-Iaving provided the clearance or relief surface of circularcross-section in rear of the cutting edges 150 on the insert 146, theinsert may be mounted with the same or greater angularity with referenceto a radial plane in a cutter or holder of the same diameter as thegrinding fixture 142. It may be mounted with less angu- Iarity ifmounted for use in a cutter or holder body having a greater diameter.

In the foregoing, the detailed description has referred to indexablecutting inserts mounted directly in recesses formed in the tool body.The present invention is equally applicable to inserts which arereceived in cartridges, and the cartridges are mounted in the tool body.Cartridges of the type referred to are disclosed in my US. Pat. No.3,371,394.

From the foregoing it will be apparent that the invention residesparticularly in initially forming commercial inserts with relief orclearance areas directly in rear of the cutting edges thereon in anoperation which avoids the necessity for grinding assembled inserts in acutter body, and which at the same time provides inserts of highaccuracy from merely commercially variable inserts by grindingoperations performed in a grinding fixture of the required accuracy.This of course requires only that the cutter body have the requisiteaccuracy provided in its insert or cartridge locating seats or pockets.

From the foregoing it will be noted that the invention is characterizedparticularly in that the edges of the inserts (as opposed to the flatparallel side surfaces) are modified by being ground to provide asurface of revolution located directly in rear of the cutting edgesdefined by the intersection between the generally flat edge surfaces anda flat side surface. These surfaces of revolution have the generatingaxis thereof located in or parallel to and spaced slightly from theplane occu pied by the flat side surface of the insert, and locatedbeyond the edge or edges of the insert opposite to the cutting edgeadjacent which the surface of revolution is provided. Thus, in thesimplest possible case, as illustrated in FIG. 6, the axis 64 of therelieved surface of revolution in rear of the cutting edge extends inthe plane of the front face 66 thereof. In FIG. 8 the generating axis ofthe surface of revolution is parallel to the plane 80 containing theforward cutting face of the insert 74. As a result of the foregoing itwill be observed that in all cases, including the case illustrated inFIG. 13 in which the surface of revolution generated during the spingrinding is conical, that the surface of revolution is of substantiallyarcuate cross-section in a plane intersecting the particular cuttingedge and perpendicular to the axis about which the cutting insertrotates while performing the cutting operation.

From the foregoing description it will of course be apparent that a setof identical and interchangeable cutting inserts is provided, each ofwhich has a properly relieved cutting edge adjacent each of its corners,the cutting edge having a flat side of the insert as its cutting faceand the relieved surface immediately in rear of the cutting edge beingthe surface of revolution provided as described herein.

What I claim as my invention is:

l. A pre-spun ground indexable cutting insert having opposed fiatparallel side surfaces and a plurality of generally flat intersectingedge surfaces, the intersection between a flat side surface and one ofthe edge surfaces defining a cutting edge, the flat side surfaceconstituting the cutting face of the insert for said cutting edge, thesaid one edge surface constituting the relief or clearance surfacethereof, the improvement which comprises providing that portion of theedge surface directly in rear of the cutting edge which constitutes therelief or clearance surface for the aforesaid cutting edge in the formof a surface of revolution about an axis at least closely adjacent tothe plane occupied by the said cutting face and spaced beyond the edgeor edges of said insert opposite to the edge surface thereof whoseintersection with the cutting face defines the aforesaid cutting edge,said surface of revolution being of substantially arcuate cross-sectionin a plane intersecting the said cutting edge and generallyperpendicular to the axis about which said insert is rotated when saidcutting edge is in cutting position, and providing atn sssssss emanates.c. of revolution is cylindrically formed.

3. An insert as defined in claim 1 in which the surface of revolution isconically formed.

4. An insert as defined in claim 1 in which the insert is rotated aboutan axis to cause the cutting edge to generate an imaginary surface ofcircular cross-section, and in which the surface of revolution divergesinwardly rearwardly of the cutting edge from such imaginary surface.

5. An insert as defined in claim 1 in which the said surface ofrevolution extends along the edge surface of the insert from a comerthereof to a point intermediate adjacent corners of the insert.

6. An insert as defined in claim 5 in which the surfaces of circularcross-section are generally triangular in outline.

7. An insert as defined in claim 1 in which each comer of the insert isprovided at one side thereat with an identical surface of revolutionmodification of the edge surface thereof.

8. An insert as defined in claim 1 in which the edge surfaces of theinsert occupy planes intersecting both side surfaces thereof at rightangles, and in which each corner of the insert is provided at both sidesthereof with an identical surface of revolution modification of the edgesurface thereof.

1. A pre-spun ground indexable cutting insert having opposed flatparallel side surfaces and a plurality of generally flat intersectingedge surfaces, the intersection between a flat side surface and one ofthe edge surfaces defIning a cutting edge, the flat side surfaceconstituting the cutting face of the insert for said cutting edge, thesaid one edge surface constituting the relief or clearance surfacethereof, the improvement which comprises providing that portion of theedge surface directly in rear of the cutting edge which constitutes therelief or clearance surface for the aforesaid cutting edge in the formof a surface of revolution about an axis at least closely adjacent tothe plane occupied by the said cutting face and spaced beyond the edgeor edges of said insert opposite to the edge surface thereof whoseintersection with the cutting face defines the aforesaid cutting edge,said surface of revolution being of substantially arcuate cross-sectionin a plane intersecting the said cutting edge and generallyperpendicular to the axis about which said insert is rotated when saidcutting edge is in cutting position, and providing cutting clearancedirectly in rear of said cutting edge.
 2. An insert as defined in claim1 in which the surface of revolution is cylindrically formed.
 3. Aninsert as defined in claim 1 in which the surface of revolution isconically formed.
 4. An insert as defined in claim 1 in which the insertis rotated about an axis to cause the cutting edge to generate animaginary surface of circular cross-section, and in which the surface ofrevolution diverges inwardly rearwardly of the cutting edge from suchimaginary surface.
 5. An insert as defined in claim 1 in which the saidsurface of revolution extends along the edge surface of the insert froma corner thereof to a point intermediate adjacent corners of the insert.6. An insert as defined in claim 5 in which the surfaces of circularcross-section are generally triangular in outline.
 7. An insert asdefined in claim 1 in which each corner of the insert is provided at oneside thereat with an identical surface of revolution modification of theedge surface thereof.
 8. An insert as defined in claim 1 in which theedge surfaces of the insert occupy planes intersecting both sidesurfaces thereof at right angles, and in which each corner of the insertis provided at both sides thereof with an identical surface ofrevolution modification of the edge surface thereof.